Interrupted pulsing circuit for audible signaling

ABSTRACT

The interrupted operation of a circuit utilized for energizing a speaker system utilized as a buzzer. A two stage relaxation oscillator circuit is utilized wherein the frequency of one oscillator is much higher than the frequency of the other oscillator. The charging rate of the circuitry within the higher frequency oscillator is slaved to the charging rate of the lower frequency oscillator until the discharge of the circuitry within the higher frequency oscillator, the signals from which are differentiated for application to the speaker. After the lower frequency oscillator discharges, the charging cycle begins again thereby providing an interrupted supply of signals to energize the speaker.

United States Patent Shuey [54] INTERRUPTED PULSING CIRCUIT FOR AUDIBLE SIGNALING [72] Inventor: David R. Shuey, Webster, N.Y. [73] Assignee: Xerox Corporation, Fairfield, Conn. [22] Filed: May 11, 1970 [21] A pl. No.: 36,225

[151 3,686,666 [4 1 Aug. 22, 1972 3,284,796 11/1966 Borsattino ..340/384 E Primary Examiner-Harold l. Pitts Attorney-James J. Ralabate, Franklyn C. Weiss and John E. Beck [57] ABSTRACT The interrupted operation of a circuit utilized for energizing a speaker system utilized as a buzzer. A two stage relaxation oscillator circuit is utilized wherein the frequency of one oscillator is much higher than the frequency of the other oscillator. The charging rate of the circuitry within the higher frequency oscillator is slaved to the charging rate of the lower frequency oscillator until the discharge of the circuitry within the higher frequency oscillator, the signals from which are differentiated for application to the speaker.

After the lower frequency oscillator discharges, the

charging cycle begins again thereby providing an interrupted supply of signals to energize the speaker.

5 Claims, 5 Drawing Figures LOGIC CONTROL Patented Aug. 22, 1972 OSC 2 Sheets-Sheet 1 I50 HZ I00, RELAX PULSE 08C GEN T SPKR LOGIC CONTROL FIG. I

LOGIC CONTROL FIG. 2

INVENTOR. DAVID R. SHUEY A T TORNEY Patented Aug. 22, 1972 3,686,666

2 Sheets-Sheet 2 FIG. 3a

FIG. 3b

4-9-- V V V 3 V: 6--

FIG. 3a

INTERRUPTED PULSING CIRCUIT FOR AUDIBLE SIGNALING BACKGROUND OF THE INVENTION Many circuits have been designed for the operation of a speaker operated as a buzzer system. Such circuits include the energizing of a one-shot multivibrator which enables and disables a sine wave supply to an external speaker. However, it is sometimes desired to low duty cycle of the output circuitry with no extraneous noise generation to disrupt associated circuitry.

OBJECTS OF THE INVENTION It is, therefore, an object of the present invention to provide an improved interrupted pulsing circuit.

It is another object of the present invention to provide a two-stage relaxation oscillator circuit for providing interrupted enabling signals to an output utilization device.

It is another object of the present invention to provide a relaxation oscillator circuit for providing enabling signals to an external speaker system operated as a buzzer with low power and a very low duty cycle.

It is another object of the present invention to provide a two-stage relaxation oscillator circuit for providing intermittent, i.e., interrupted, pulses for the enabling of a speaker utilized in a buzzer system.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention as well as other objects and further features thereof, reference is made to the following detailed description taken in conjunction with the accompanying drawings wherein:

F l6. 1 is a block diagram of the circuitry embodying the principles of the present invention;

FIG. 2 is a detailed schematic diagram of the circuitry depicted in the block diagram of FIG. 1; and

FIG. 3 are curves helpful in understanding the principles of the invention set forth in FIGS. 1 and 2.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 shows the overall block diagram of the present invention in which there are two relaxation oscillators. The first is a l hz. oscillator and the other is a 150 hz. oscillator under control of the logic control input. These two relaxation oscillators are under con trol of various components therein which allows for a 150 hz. signal to be applied to the pulse generator at least once every second in response to the l hz. oscillator. The pulse generator generates the 100 microsecond signals in response to the relaxation oscillators and drives the speaker by means of the driver circuit shown in FIG. 1.

FIG. 2 shows the schematic diagram of the circuit shown in FIG. 1. The logic control input is the energizing signal which, if grounded, inhibits the operation of the circuit, while when in an ungrounded or open condition, allows the circuit to operate in the manner to be hereinafter described. When the logic control input is in an open or ungrounded condition, transistor O8 is nonconducting which effectively unshorts capacitor C1. Current then flows from the positive voltage supply through resistor R4 to begin charging capacitor C1. FIG. 3 shows the curves of the path of the signal potentials applied to the circuit. Thus, signal V shows the path of the signal potential rising from the l4 supply voltage to the operating potential of the Schmitt trigger circuit comprising transistors Q1 and Q2. At the same time that capacitor C1 is charging, capacitor C2 is charging through resistor R5. As seen in FIG. 3, the charging rates of capacitors Cl and C2 are essentially the same, the only difference being the voltage drop across diode D2 on the charging rate of capacitor C1. At the same time that resistors R4 and R5 are charging capacitors C1 and C2, current is flowing through resistors R1 and R2 to ground. If, for example, the positive voltage supply is at +14 volts and the negative voltage supply is l4 volts, then resistors R1 and R2 as a voltage divider could have the value of +5 volts at point B. In FIG. 3, line V indicates this condition.

While capacitors C1 and C2 are charging to their respective voltages, current is also flowing through resistor R6, diode D4, and the base-emitter junction of transistor Q5 to ground. The value of resistor R6 is. such that at point D in FIG. 2, the voltage is at, for example, 1.2 volts. When the capacitor C2 has been charged through resistor R5 to a value approximately 1.2 volts, the potential is applied through diode D3 to the emitter of transistor Q3. With the emitter of transistor Q3 now at a higher voltage than the base of transistor Q3, i.e., point D, the Schmitt trigger circuit comprising transistors Q3 and Q4 are enabled thereby discharging capacitor C2. Transistors Q3 and Q4 operate in a bootstrap manner where the current flows from capacitor C2 through diode D3 through the emitter, base and collector elements of transistor Q3 through the base emitter junction of transistor O4 to the minus voltage supply. With transistor Q4 now in an on condition, transistors Q3 and O4 are more strongly enabled and quickly allow the discharge of capacitor C2. The discharge of capacitor C2 is seen in FIG. 3a as in the curve V representing the discharge as capacitor C2 falls to the 14 voltage supply when the charging curve reaches the line representing the voltage at point V or 1.2 volts.

During this discharge cycle, capacitor C1 continues charging to a value of approximately 5 volts at point A which through diode D1 fires the trigger circuit comprising transistors Q1, Q2 and resistor R3 due to the fact that the voltage on the emitter of transistor O2 is now at a higher value than the voltage between resistors R1 and R2, i.e., point B. This situation can be seen in reference to FIG. 3 wherein the upper curve V continues charging to the line representing the potential V or 5 volts.

The charging rate for capacitors Cl and C2 is determined by the RC time constant of resistor R4 in parallel with resistor R5 multiplied by the value of capacitance of capacitor C1 in parallel with capacitor C2. After capacitor C2 discharges through transistors Q3 and Q4 the time constant of capacitor C1 charging from potential V to the 5-volt mark at potential V,, is determined by only resistor R4 multiplied by capacitor C1. When capacitor C2 is charging by itself after initial discharge through transistors Q3 and Q4, the time constant is determined by resistor R multiplied by capacitor C2. Thus, resistor value R5 and capacitor C2 are chosen that the cycle rate is much higher than that of resistor R4 and capacitor CI. Thus, capacitor C2 will charge and discharge at a much higher rate than capacitor C]. This is seen in FIG. 3 where capacitor C2 cycles many times prior to the initial cycling of capacitor C1.

FIG. 3b shows the voltage as appearing at point D in FIG. 2. The output from transistors Q3 and Q4 are differentiated by resistor R6 and capacitor C3 as shown by thenegative voltage spikes shown in FIG. 3b. These signals are applied to transistor Q5 which is coupled to the positive potential source through resistor R7. Capacitor C4 rounds off the leading edges of the pulses generated by the differentiator to allow a more pleasing sound to be emanated from the speaker. Transistors Q6 and Q7 in conjunction with resistor R8 comprise a Darlington circuit which is used to supply the necessary current and equalization for driving the speaker.

Referring now specifically to FIG. 3, FIG. 3a shows the curves as hereinabove set forth as defined at various places in the circuitry of FIG. 2. Thus, signal V, is a dotted line showing the curve of capacitor C1 charging through resistor R4. After capacitor C1 charges to +5 volts, capacitor C1 discharges through transistors Q1 and Q2 and the cycle begins again. The solid line curve, V, in FIG. 3a is the charging curve for capacitor C2 at point C of FIG. 2 through resistor R5. At 1.2 volts, capacitor C2 discharges through transistors Q3 and Q4 thereby discharging to l4 volts. The curve V now charges along a different RC time constant due to the fact that capacitor C1 is now being charged only through resistor R4. Potential curve V, now is independent of the charging of capacitor C1 and delineates the charging curves for capacitor C2 alternately charging and discharging through transistors Q3 and Q4. Only four of such cycles are shown for simplicity, but it is apparent that the number of such charging cycles is dependent upon the RC time constant of resistors R5 and capacitor C2 and the cycle time of charging and discharging thereof. After capacitor C1 discharges through transistors Q1 and Q2, the cycle begins again for as long as the circuit is energized.

FIG. 3b shows the action of the differentiator circuit comprising resistor R6 and capacitor C3 on curve V in FIG. 3a. That is, the differentiator circuit differentiates the negative spikes in V, in FIG. 3a giving the negative spikes V through V FIG. 3c shows the signals at the output of transistor Q5 at point B. That is, the negative signal spikes in FIG. 3b deenergize or turn off transistor Q5 thereby generating the signals V through V in FIG. 3c. The leading edge of these signals are rounded off to show the effect of feedback capacitor C4 which smoothes out any ringing effect in the generation of the signals in FIG. 3c. The signals seen in FIG. 30 are then coupled to the Darlington amplifier comprising transistors Q6 and Q7 which are utilized for equalizing the impedance between the circuitry and the speaker and for providing a current gain for driving the speaker. It can be seen, therefore, that the speaker will not be energized during the initial charging of capacitors C1 and C2 because there are no negative spike signals to be differentiated by resistor R6 and capacitor C3. Once capacitor C2 has discharged, then capacitor C2 is independent in its charging and discharging cycle, because diode D2 is back biased, and will continue this action of charging and discharging until capacitor C1 has discharged through its discharge path of transistors 01 and Q2. The negative spikes caused by the discharge of capacitor C2 is differentiated and amplified and applied to the speaker for the enabling thereof to generate the intermittent buzzing sound desired.

In FIG. 3c it is seen that each of the signals V is approximately microseconds in duration while the interval between the signals is 6.6 milliseconds. While the current drain during the pulses is relatively high, in regards to the circuit, the duty cycle of the signals with respect to the signal width to the cycle spacing determines a low duty cycle which has a low average value of current, therefore. At any time during the operation of the circuit, if the signal on the logic control circuit input is ever coupled to ground, the charging and discharging action of capacitor C1 is terminated and the operation of the speaker is similarly terminated.

In the foregoing there has been disclosed apparatus for providing an intermittent signal to be applied to a speaker as a buzzing system with low cost and low average power drain. While the circuit has been described in conjunction with specific voltage and time values, it would be apparent to one skilled in the art that such values could be changed by specific designation of circuit component values within the principles of the present invention. Therefore, while the invention has been described with reference to a specific embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt to a particular situation without departing from the essential teachings of the invention.

What is claimed is:

1. An interrupted pulsing circuit comprising:

a first relaxation oscillator circuit means comprising a first circuit for charging and discharging at a first rate,

a second relaxation oscillator circuit means comprising a second circuit for charging and discharging at a second rate, said second rate being much higher than said first rate,

means for coupling said first relaxation oscillator circuit means to said second relaxation oscillator circuit means wherein the charging rate of said second relaxation oscillator circuit means is slaved to the charging rate of said first relaxation oscillator circuit means until said second relaxation oscillator circuit means discharges and thenceforth continues to independently charge and discharge until said first relaxation oscillator circuit means discharges and thus recycles the interrupted pulse generation,

difierentiating circuit means coupled to said second relaxation oscillator circuit means for differentiating the discharge transitions of the charging and discharging cycles thereof,

means coupled to said differentiating circuit means for generating the output pulse, and

speaker means for generating intermittent buzzing sounds in response to the output generated pulses. 2. An interrupted pulsing circuit comprising: a first resistor-capacitor charging circuit, first means for discharging said first capacitor when the charge on said first capacitor reaches a predetermined value, a second resistor-capacitor charging circuit, second means for discharging said second capacitor when the charge on said second capacitor reaches a predetermined value, the charging and discharging cycle rate of the second resistor-capacitor circuit being substantially higher than the charging and discharging cycle rate of the first resistorcapacitor circuit, diode means for coupling said first resistor-capacitor charging circuit to said second resistor-capacitor charging circuit wherein the charging rate of said second resistor-capacitor circuit follows the charging rate of said first resistor-capacitor circuit until said second resistor-capacitor circuit discharges thereby continuing to independently charge and discharge until said first resistor-capacitor circuit discharges thus recycling the generation of the interrupted pulses, differentiating circuit means coupled to said second resistor-capacitor circuit for differentiating the discharge transitions of the charge and discharge signals generated thereby, means coupled to said differentiating circuit means for generating the interrupted output pulses, wherein said first discharging means is a first trigger circuit and wherein said second discharging means is a second trigger circuit, said second trigger circuit discharging said second capacitor at a lower charge than said first trigger circuit discharges said first capacitor, wherein said diode means is accordingly back biased to allow said second resistor-capacitor charging circuit and said second discharging means to operate independently until the discharge of said first capacitor. 3. The circuit as set forth in claim 2 including: speaker means for generating intermittent buzzing signals in response to the output generated pulses. 4. An interrupted pulsing circuit comprising, first oscillator circuit means for generating signals of a first frequency, second oscillator circuit means coupled to said first oscillator circuit means for generating signals of a second frequency, said second frequency being higher than said first frequency, wherein the operation of said second oscillator circuit means is periodically interrupted at the rate of and in response to the signals of said first frequency, and means for differentiating said second frequency signals to generate output pulses at said second frequency periodically interrupted at the rate of said first frequency, said first oscillator circuit means comprising a first relaxation oscillator for charging and discharging at a first rate, and said second oscillator circuit means comprising a second relaxation oscillator for charging and discharging at a second rate, the pulsing circuit including means for coupling said first relaxation oscillator to said second relaxation oscillator wherein the charging rate of said second relaxation oscillator is slaved to the charging rate of said first elaxatio oscillato ntil sgid econd relaxation OSCll ator dlsc arges an t ence ort continues to independently charge and discharge until said first relaxation oscillator discharges and thus recycles the interrupted pulse generation, said first relaxation oscillator comprising a first resistor-capacitor charging circuit, and first means for discharging said first capacitor when the charge on said first capacitor reaches a predetermined value, said second relaxation oscillator comprising a second resistor-capacitor charging circuit and second means for discharging said second capacitor when the charge on said second capacitor reaches a predetermined value, the charging and discharging cycle rate of the second resistor-capacitor circuit being substantially higher than the charging and discharging cycle rate of the first resistor-capacitor circuit, and said coupling means comprising diode means.

5. The pulsing circuit set forth in claim 4 wherein said means for differentiating said second frequency signals comprises a differentiating circuit coupled to said second relaxation oscillator for differentiating the discharge transitions of the charging and discharging cycles thereof, means coupled to said differentiating circuit for generating the output pulses, speaker means for generating intermittent buzzing sounds in response to said output generated pulses, and wherein said first discharging means is a first trigger circuit and wherein said second discharging means is a second trigger circuit, said second trigger circuit discharging said second capacitor at a lower charge than said first trigger circuit discharges said first capacitor, wherein said diode means is back biased to allow said second resistorcapacitor charging circuit and said second discharging means to operate independently until the discharge of said first capacitor. 

1. An interrupted pulsing circuit comprising: a first relaxation oscillator circuit means comprising a first circuit for charging and discharging at a first rate, a second relaxation oscillator circuit means comprising a second circuit for charging and discharging at a second rate, said second rate being much higher than said first rate, means for coupling said first relaxation oscillator circuit means to said second relaxation oscillator circuit means wherein the charging rate of said second relaxation oscillator circuit means is slaved to the charging rate of said first relaxation oscillator circuit means until said second relaxation oscillator circuit means discharges and thenceforth continues to independently charge and discharge until said first relaxation oscillator circuit means discharges and thus recycles the interrupted pulse generation, differentiating circuit means coupled to said second relaxation oscillator circuit means for differentiating the discharge transitions of the charging and discharging cycles thereof, means coupled to said differentiating circuit means for generating the output pulse, and speaker means for generating intermittent buzzing sounds in response to the output generated pulses.
 2. An interrupted pulsing circuit comprising: a first resistor-capacitor charging circuit, first means for discharging said first capacitor when the charge on said first capacitor reaches a predetermined value, a second resistor-capacitor charging circuit, second means for discharging said second capacitor when the charge on said second capacitor reaches a predetermined value, the charging and discharging cycle rate of the second resistor-capacitor circuit being substantially higher than the charging and discharging cycle rate of the first resistor-capacitor circuit, diode means for coupling said first resistor-capacitOr charging circuit to said second resistor-capacitor charging circuit wherein the charging rate of said second resistor-capacitor circuit follows the charging rate of said first resistor-capacitor circuit until said second resistor-capacitor circuit discharges thereby continuing to independently charge and discharge until said first resistor-capacitor circuit discharges thus recycling the generation of the interrupted pulses, differentiating circuit means coupled to said second resistor-capacitor circuit for differentiating the discharge transitions of the charge and discharge signals generated thereby, means coupled to said differentiating circuit means for generating the interrupted output pulses, wherein said first discharging means is a first trigger circuit and wherein said second discharging means is a second trigger circuit, said second trigger circuit discharging said second capacitor at a lower charge than said first trigger circuit discharges said first capacitor, wherein said diode means is accordingly back biased to allow said second resistor-capacitor charging circuit and said second discharging means to operate independently until the discharge of said first capacitor.
 3. The circuit as set forth in claim 2 including: speaker means for generating intermittent buzzing signals in response to the output generated pulses.
 4. An interrupted pulsing circuit comprising, first oscillator circuit means for generating signals of a first frequency, second oscillator circuit means coupled to said first oscillator circuit means for generating signals of a second frequency, said second frequency being higher than said first frequency, wherein the operation of said second oscillator circuit means is periodically interrupted at the rate of and in response to the signals of said first frequency, and means for differentiating said second frequency signals to generate output pulses at said second frequency periodically interrupted at the rate of said first frequency, said first oscillator circuit means comprising a first relaxation oscillator for charging and discharging at a first rate, and said second oscillator circuit means comprising a second relaxation oscillator for charging and discharging at a second rate, the pulsing circuit including means for coupling said first relaxation oscillator to said second relaxation oscillator wherein the charging rate of said second relaxation oscillator is slaved to the charging rate of said first relaxation oscillator until said second relaxation oscillator discharges and thenceforth continues to independently charge and discharge until said first relaxation oscillator discharges and thus recycles the interrupted pulse generation, said first relaxation oscillator comprising a first resistor-capacitor charging circuit, and first means for discharging said first capacitor when the charge on said first capacitor reaches a predetermined value, said second relaxation oscillator comprising a second resistor-capacitor charging circuit and second means for discharging said second capacitor when the charge on said second capacitor reaches a predetermined value, the charging and discharging cycle rate of the second resistor-capacitor circuit being substantially higher than the charging and discharging cycle rate of the first resistor-capacitor circuit, and said coupling means comprising diode means.
 5. The pulsing circuit set forth in claim 4 wherein said means for differentiating said second frequency signals comprises a differentiating circuit coupled to said second relaxation oscillator for differentiating the discharge transitions of the charging and discharging cycles thereof, means coupled to said differentiating circuit for generating the output pulses, speaker means for generating intermittent buzzing sounds in response to said output generated pulses, and wherein said first discharging means is a first trigger circuit and wherein said second discharging means is a second trigger circuit, said second trigger circuit dIscharging said second capacitor at a lower charge than said first trigger circuit discharges said first capacitor, wherein said diode means is back biased to allow said second resistor-capacitor charging circuit and said second discharging means to operate independently until the discharge of said first capacitor. 